(Minecraft Java 1.14) How are bossbars ordered, and can I make sure one of them always stays at the top?

I did some testing in 1.14.3 and the bossbars are in the order that they were added to a player, the first one you add to a player will be the highest for that player.

I haven´t tried this in multiplayer, so a bossbar may move all the way down to the list when you try to add it to @a again, to add more players, other than that it should always stay at the top if it is at the top.

Edit:

This does apparently not survive reloading the world and requires more testing.

Update:

The bossbar with the id 0 seems to always be on top after reloading the map. After that 2, 1, 4, 3, 6, 5,... (+2; -1; +2; -1;...)
This may still require more testing.